Various electronic apparatuses, particularly mobile terminals, such as a mobile phones, have recently includes operation panels illuminated by light emitting diodes or EL elements to facilitate identifying and activating push buttons and display sheets even in dark environment. Movable contact assemblies and switches used for these apparatuses are demanded to use easily and to be illuminated in various manners.
FIGS. 11 and 12 are a sectional view and a plan view of conventional switch 601, respectively. Light guide sheet 104 includes material sheet 101 made of light-transmissible film. Illumination portions 102A, 102B, and 102C each including plural projections are provided on an upper surface of material sheet 101.
Slit 103A having a strip shape and a squared U-shape is provided in material sheet 101 around illumination portion 102A. Slits 103B having a strip shape and an L-shape is provided in material sheet 101 around illumination portion 102C. Slits 103A and 103B passes between the upper surface and a lower surface of material sheet 101.
Base sheet 105 has a film shape. Plural movable contacts 106 have substantially a dome shape and are made of thin metal plates. An outer periphery of base sheet 105 is stuck onto the lower surface of light guide sheet 104 with an adhesive. Upper surfaces of plural movable contacts 106 are stuck onto a lower surface of base sheet 105 directly beneath illumination portions 102A, 102B, and 102C, thus providing movable contact assembly 107.
Plural circuit patterns are provided on upper and lower surfaces of circuit board 108. Plural fixed contacts 109 each including center fixed contact 109A and outer fixed contact 109B are provided the upper surface of circuit board 108. Center fixed contact 109A has substantially a circular shape. Outer fixed contact 109B has substantially a horseshoe shape or a ring-shape surrounding center fixed contact 109A.
Movable contact assembly 107 is stuck onto the upper surface of circuit board 108. An outer periphery of movable contact 106 is mounted onto outer fixed contact 109B. The center of the lower surface of movable contact 106 faces center fixed contact 109A with a predetermined interval between them.
Plural light emitters 110A and 110B implemented by a light-emitting device, such as a light emitting diode, are mounted on the upper surface of circuit board 108 at a side of light guide sheet 104. Light emitters 110A and 110B have light-emitting surface facing end surfaces 101C and 101D of material sheet 101, respectively.
Display sheet 111 is light-transmissible and has a film shape. Light blocking portion 111A is formed on a lower surface of display sheet 111 by, e.g. printing. Predetermined positions of light blocking portion 111A are hollowed in shapes, such as characters or symbols, to form plural display portions 111B. Display portions 111B are located directly above illumination portions 102A, 102B, and 102C of light guide sheet 104.
Switch 601 is installed to an operation panel of an electronic apparatus. Center fixed contact 109A, outer fixed contact 109B, and light emitters 110A and 110B are connected with an electronic circuit of the apparatus via the circuit patterns.
In FIG. 11, center fixed contact 109A is electrically disconnected from outer fixed contact 109B. When an operator presses down display portion 111B of display sheet 111, light guide sheet 104 and base sheet 105 sag to apply a pressing force onto the center part of movable contact 106. When the pressing force exceeds a predetermined level, movable contact 106 has its shape elastically reversed downward being accompanied with a click feel, and the center of the lower surface of movable contact 106 contacts center fixed contact 109A. This contact connects center fixed contact 109A electrically with outer fixed contact 109B via movable contact 106.
When the pressing force applied to display sheet 111 is released, movable contact 106 has its shape elastically reverse upward by an elastic self-restoring force, thus removing the center of the lower surface of movable contact 106 from center fixed contact 109A. This operation disconnects center fixed contact 109A electrically from outer fixed contact 109B.
The electronic circuit of the apparatus switches functions of the apparatus and supplies power to light emitters 110A and 110B according to electrical connection and disconnection between fixed contacts 109A and 109B. Upon the power being supplied, light emitters 110A and 110B emit light. In the case that light emitter 110A emits orange light, and that light emitter 110B emits green light, the orange light enters in light guide sheet 104 from end surface 101C of light guide sheet 104, and the green light enters in material sheet 121 of light guide sheet 125 from end surface 101D which is different from end surface 101C of light guide sheet 104. These lights transmit in material sheet 101 while reflecting.
The lights entering in material sheet 101 are diffused and reflected at plural illumination portions 102A, 102B, and 102C on the upper surface of material sheet 101 to illuminate display portion 111B of display sheet 111 from beneath. If the lights emitted by light emitters 110A and 110B have the above-described colors, a part of display portion 111B directly above illumination portion 102A is illuminated in orange color, and parts of display portion 111B directly above illumination portions 102B and 102C are illuminated in green color. This operation allows the operator to identify a displayed item, such as characters and symbols, even in dark environment and to operate the apparatus easily.
Slits 103A and 103B provided around illumination portions 102A and 102C block the light transmitting in material sheet 101. That is, the orange light from light emitter 110A reaches illumination portion 102A. A part of the reaching light is diffused and reflected to illuminate upward, and the other part of the light transmits from illumination portion 102A further along material sheet 101. The part of the light transmitting via illumination portion 102A is blocked by slit 103A having substantially the squared U-shape, thereby being prevented from reaching other illumination portions, such as illumination portion 102B or 102C. The green light emitted from light emitter 110B reaches illumination portion 102B. A part of the reaching light is diffused and reflected to illuminate upward, and the other part of the light transmits from illumination portion 102B further along material sheet 101. The part of the light transmitting via illumination portion 102B is blocked by slit 103B having substantially the L-shape. This prevents the lights having these colors from being mixed, and prevents portion which is not to be illuminated from being illuminated.
FIG. 13 is a plan view of light guide sheet 104. In processes of producing movable contact assembly 107 and switch 601, as shown in FIG. 13, illumination portions 102A and 102C on material sheet 101 may curl up and down, hence being prevented from sticking onto the upper surface of material sheet 105 and thus reducing workability. If material sheet 101 is strongly bent at this moment, the bent portion thereof can cause unevenness of illumination upon being illuminated.